The present invention relates to an engine system, particularly for vehicles. Current “hybrid” vehicles include an internal combustion engine that is supplemented by one or more electric motors powered by electrical batteries. The batteries are recharged by recouping some of the energy that would otherwise be lost during braking, i.e. regenerative braking. One problem with current hybrids is that the batteries cannot be charged quickly and therefore cannot recoup all the large amounts of energy that is available in a short time during braking.